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Reservoir quality is one of the important geological factors controlling the development of tight oil in the Honghe oilfield, Ordos Basin, northwestern China. Analyses of core, well logging, mud logging and geophysical data as well as thin sections (casting and fluorescence) were combined with testing methods (such as grain size analysis, constant-rate mercury injection, and scanning electron microscopy) to characterize the micropore–throat development in reservoirs of the eighth member of Yanchang Formation in the oilfield. From the perspective of sedimentation and diagenesis, the mechanisms causing reservoir quality difference were explored and a method for characterizing reservoir quality difference and distribution was proposed. The results show that complex and diverse pore–throat configurations and multi-scale throat development are the microscale manifestations of reservoir quality differences in the member. Three types of pore–throat combinations are recognized, including intergranular pore-wide lamellar throat, intergranular and intragranular pore-wide lamellar throat, and intergranular/clustered micropore-wide lamellar throat. Different diagenesis processes and intensities under the control of sedimentary conditions determine the differential development of the reservoirs. Diagenetic facies are the indicators of reservoir quality. Diagenetic facies with chlorite cementation-moderate dissolution indicates reservoirs with the most ideal physical properties for hydrocarbon accumulation, while that with moderate calcite and kaolinite cementations are usually observed in reservoirs with less ideal physical properties. Reservoirs with the worst physical properties often correlate with diagenetic facies with strong calcite cementation and compaction facies. A multi-level constrained method under the control of sedimentation and diagenetic facies is proposed for characterizing tight reservoir quality difference in the member. The spatial distribution of sedimentary elements is analyzed through sedimentary configurations, the diagenetic facies distribution is constrained by sedimentary elements and the reservoir quality distribution is predicted with constraint of diagenetic facies. It suggests that the high-quality reservoirs in the member occur vertically in the middle of thick channel sandstone, while poor reservoirs occur in the upper or lower parts of the channel sandstone due to intensive compaction and cementation. Laterally, the quality of reservoirs enhances along the channels with a change in shape to lens or strips along the middle and downstream sections.

Mud logging is frequently performed during oil and gas operations for determining the position of hydrocarbons and accurately assessing the geophysical properties of the formation based on the stud...

Tight sandstone reservoirs are generally characterized by complex reservoir quality, non-Darcy flow, and strong heterogeneity. Approaches utilized for evaluating physical property cutoffs of conventional reservoirs maybe inapplicable. Thus, a comprehensive investigation on physical property cutoffs of tight sandstone reservoirs is crucial for the reserve evaluation and successful exploration. In this study, a set of evaluation approaches take advantage of field operations (i.e., core drilling, oil testing, and wireline well logging data), and simulation experiments (i.e., high-pressure mercury injection-capillary pressure (MICP) experiment, oil-water relative permeability experiment, nuclear magnetic resonance (NMR) experiment, and biaxial pressure simulation experiment) were comparatively optimized to determine the physical property cutoffs of effective reservoirs in the Upper Triassic Chang 6, Chang 8 and Chang 9 oil layers of the Zhenjing Block. The results show that the porosity cutoffs of the Chang 6, Chang 8, and Chang 9 oil layers are 7.9%, 6.4%, and 8.6%, and the corresponding permeability are 0.08 mD, 0.05 mD, and 0.09 mD, respectively. Coupled with wireline well logging, mud logging, and oil testing, the cut-off of the thickness of single-layer effective reservoirs are approximately 3.0 m, 3.0 m, and 2.0 m, respectively. Depending on the cutoffs of critical properties, a superimposed map showing the planar distribution of the prospective targets can be mapped, which may delineate the effective boundary of prospective targets for petroleum exploration of tight sandstone reservoirs.

Effect of depletion rate on wellbore stability due to production of oil from hydrocarbon-bearing reservoirs is important and can result in a reduction of the reservoir pore pressure. A reduction in the reservoir pressure, in turn, results in a change in the stresses acting within the reservoir. If these changes are not well analyzed and applied in future calculations, we may be unsuccessful in some cases such as drilling infill wells or extended wells, forecast of sand production and optimum flow rate, preventing of casing collapse, etc. Therefore, knowing the stresses around the well at every stage of production is fundamental to the next calculations. In this paper, we recognized these changes in near-wellbore stresses using data from logging (image log, dipole sonic, full set log, mud log), production data, information from kick, blow out, loss etc. and determined it using Techlog software and theoretical calculations. Three wells of two huge oilfields of SW Iran were investigated after depletion or production for long years. In each well, state of stresses were calculated in cases of safe drilling mud weight using log data and theoretical equations. At the end effect of depletion rate on wellbore stability was investigated in these three wells.

The overall development of the top of the gas reservoir of the Dengying Formation, Upper Sinian in the Anyue Gas Field of the Sichuan Basin, has been deployed, and the inner Dengying Formation is the next potential succession layer. However, the high-quality reservoirs of inner Dengying Formation are undeveloped and cannot be identified on the seismic profiles, which restricts its deepened understanding, exploration and development. In this paper, the logging and seismic response characteristics of high-quality reservoirs were analyzed using the mud logging and well logging data of the Anyue Gas Field, and a seismic response model for high-quality reservoir was established by means of seismic forward modeling. Then, the target processing was carried out for the problem of weak effective signals. Finally, the plane distribution of high-quality reservoirs of inner Dengying Formation and the favorable exploration areas were predicted. And the following research results were obtained. First, there are two types of high-quality reservoirs inside the Dengying Formation, i.e., concentrated vug type and independent cave type. Vertically, the independent cave reservoirs are mainly distributed within 100 m above the mudstone floor of the third Member of Dengying Formation. Horizontally, karst zones are developed along the bed. Laterally, they are scattered and beaded. And the scale is small. Second, seismic response of high-quality reservoirs inside the carbonate rocks is characterized by single-peak concealed “beaded” reflection, whose peak energy is relatively weak and can be easily covered by the noise of seismic data. Third, deep-seated weak signal recovery and processing technology can be used to deal with the weak seismic response of high-quality cave reservoirs, improve the amplitude preservation and S/N ratio of seismic data, and obtain the beaded reflections on seismic profiles so as to realize effective identification of high-quality cave reservoirs. In conclusion, the deep-seated weak signal recovery and processing technology is proved to be operable because the achieved results conform to the drilling data and the seismic forward modeling conclusions. In addition, high-quality cave reservoirs are developed at the bottom of the fourth Member of Dengying Formation, and they are locally distributed in a large scale. Therefore, it's one of the favorable succession layers for the following natural gas exploration and development of the Anyue Gas Field. Keywords: Sichuan Basin, Anyue Gas Field, Late Sinian, Inner Dengying Formation, High-quality reservoirs, Cave, Beaded reflection, Multiple wave, Weak signal recovery, Succession layer series

In order to promote the exploration and development of oil reservoirs in northern Shaanxi, using core, mud logging and logging data, the study on the characteristics of sand bodies and sedimentary facies of Yan 8 oil layer group in X area was carried out. Based on the core description, the analysis of single-well sedimentary facies, continuous-well sedimentary facies, and planar sedimentary facies is carried out. It is believed that the Yan 8th section of the study area is a river-controlled delta plain environment, with three main developments: distributary channels, natural dikes and interbranch swamp Microphase. Vertically, the sand bodies in the Yan 8 oil layer group are discontinuous, and there are mainly distributary channels and inter-branch swamps. Horizontally, the Yan 8 oil layer group develops 10 river channels, which are distributed in a strip on the plane, and the extension direction is northwest-south east. Channel deposits constitute the main body of the sand body skeleton and are also the main oil and gas enrichment area.

The North Sea has always been a pioneer for the adoption of remote operations services (ROS) in offshore drilling applications. Drilling services such as Measurement While Drilling (MWD), Logging While Drilling (LWD) and/or mud logging (ML) have been performed with an element of ROS for over the last two decades. Early adoption of these remote services delivered initial benefits to operators such as reducing HSE risks related to the travel and accommodation of field service employees at offshore rig sites. Meanwhile service companies were able to explore the added efficiencies gained by having multi-skilled employees providing a higher level of support to customers while also gaining additional agility to manage their personnel through tighter market cycles. The mutual benefit of this early adoption created a solid foundation for ROS to expand the scope of influence in drilling operations to include Directional Drilling (DD). Despite the maturity of ROS within a select community of operators in the North Sea, the industry standard for service delivery in offshore operations has continued to require field service employees to perform DD, MWD, and LWD services at rig sites until this past year. With the COVID-19 pandemic in 2020, operators and service companies were quickly and abruptly confronted with the challenges of new HSE regulations, travel restrictions, and increased financial scrutiny. ROS presented a tailored solution to not only sustain business continuity but also create added efficiency, consistency, and risk management. Over the course of 2020, adoption of ROS rapidly accelerated across offshore operations in the North Sea and reached up to 100% penetration in key sectors. This tremendous achievement has made a significant impact on project performance and HSE efficiencies by ensuring on time service delivery while reducing personnel on board (POB). In addition, as more operators and services companies explore ways of reducing their carbon footprints and achieving a net zero future, ROS has proven to be a way to significantly reduce carbon emissions associated with transportation and utilities of offshore personnel. This paper discusses the methods that enabled a record high adoption rate for ROS and explores the critical components of its success. It illustrates the management of change in service delivery processes, the introduction of new technology to unlock greater productivity and synergies, and the new approach to design the core competencies needed to support ROS. It also describes the need for flexible ROS service models to meet the specific project needs of various operators. The paper concludes with the numerous benefits realized through ROS such as improved performance and consistently reliable service delivery. The paper also examines the resulting carbon emission reduction, how to quantify it, and the role ROS plays in achieving a net zero emissions future.

SummaryAn advanced gas analysis heated system (AGAHS) analyzes the gas extracted from a water-based mud (WBM) to estimate the hydrocarbons contents in drilled rock formations. Operating conditions within the gas-extraction device (gas trap) such as the gas concentration in the mud, stirring velocity, mud-flow rate and temperature, and ditch-line flow rate and pressure are studied to maximize the gas-extraction efficiency in the gas trap. The operating conditions that most affect the gas-extraction efficiency are the stirring velocity and the mud-flow rate. The highest and most stable gas-extraction efficiencies are obtained at 1,680 rev/min and 1.0 L/min.

The rate of penetration (ROP) plays a major role in drilling optimization, which makes it an important area of investigation. In this work, sensitivity and statistical analysis were carried out using a big set of data gathered from over 800 wells in the Basra oil fields, Iraq. The main objective of this investigation is to assess the effect of mud weight (MW) on ROP and to provide a method for estimating the recommended range for operational mud weight based on the rock hardness. The collected data for the drilling intervals from the drilling reports for over 800 wells in the Basra oil fields, Iraq, were categorized as weak, medium, hard, and very hard, based on the unconfined compressive strength (UCS), depth, and lithology. Statistical and sensitivity analyses were conducted and correlation coefficients (CC) were developed to describe relationships between rock hardness, ROP, and MW from field data. This methodology combines data from mud logging, daily drilling reports, and geological information to investigate the relationship between ROP and MW for different rock types and strengths. Several previous studies focused directly on MW, where the effect of MW on bit conditions, and thus the ROP was clearly demonstrated. However, these studies did not take into consideration the rock hardness or lithology. There is also a strong discrepancy between results from different studies, where some studies showed an inverse relationship between MW and ROP, while other studies showed it was a direct relationship. In this study, field data have been gathered (more than 800 wells) to further investigate the relationship between MW and ROP, and how it varies with rock hardness. The results showed that MW has an inverse relationship with ROP for the weak formation with a CC of −0.57, suggesting that the MW should be maintained as minimum as possible when drilling through the weak formation. On the other hand, MW showed a direct relationship with ROP for medium, hard, and very hard formations with CC of 0.31, 0.4, and 0.42 respectively. Hence, MW has to be maintained as high as possible to maximize ROP for medium, hard, and very hard formations. Large-scale collection and interpretation of field data were collected to demonstrate the effects of MW on ROP with varying rock hardness and lithology. While field data of this scale is inherent of interest, this analysis also investigates relationships previously unexplored and extends understanding of how MW effects ROP.

This work deals with quantitative analysis of multicomponent mud logging gas based on infrared spectra. An accurate analysis method is proposed by combining a genetic algorithm (GA) and a radial basis function neural network (RBFNN). The GA is used to screen the infrared spectrum of the mixed gas, while the selected spectral region is used as the input of the RBFNN to establish a calibration model to quantitatively analyze the components of logging gas. The analysis results demonstrate that the proposed GA-RBFNN performs better than FS-RBFNN and ES-RBFNN, and our proposed method is feasible.

The Chang 81 Member, Yanchang Formation in Huanxian area, Ordos Basin, China, is a tight sandstone dominated reservoir with low porosity and low permeability. The contribution of pore fluid to well logging response is greatly reduced, and the resistivity of oil layer and water layer are close, which bring great difficulties to the fluid identification and logs interpretation. In this paper, we first analyzed the genetic mechanism of the low-resistivity oil pay layer in terms of reservoir petrological characteristics, irreducible water saturation and formation water salinity. The high content of clay and complex pore structure resulting in high irreducible saturation which leads to additional conductivity; and the formation water salinity has great difference in this area. In order to reduce the influence of the formation water salinity difference on the fluid identification, we separated the study area into normal oil pay region and low-resistivity oil pay region based on the relationship between formation water salinity and formation resistivity. Then, double apparent formation water resistivity difference method, fluid identification factor cross-plot method, full hydrocarbon mud logging and well logging hybrid method and the normal distribution method were established in two different regions, respectively. The comparison of different fluid identification methods show that full hydrocarbon mud logging and well logging hybrid method is the best method for fluid typing of oil layer, oil-water layer and water layer. Double apparent formation water resistivity difference method is not effective to distinguish the oil-water layers from the water layers and oil layers, and the normal distribution method is not applicable for distinguishing the low-resistivity oil pay. In the case study, the above methods are together used to identify the fluids of the reservoirs, and the application result indicates that comprehensive analysis of multiple methods can effectively improve the accuracy of fluid typing.

Predicting the drilling rate of penetration (ROP) is one approach to optimizing drilling performance. However, as ROP behavior is unique to specific geological conditions its application is not straightforward. Moreover, ROP is typically affected by various operational factors (e.g. bit type, weight-on-bit, rotation rate, etc.) as well as the geological characteristics of the rocks being penetrated. This makes ROP prediction an intricate and multi-faceted problem. Here we compare data mining methods with several machine learning algorithms to evaluate their accuracy and effectiveness in predicting ROP. The algorithms considered are: artificial neural networks (ANN) applying a multi-layer perceptron (MLP); ANN applying a radial basis function (RBF); support vector regression (SVR), and an hybrid MLP trained using a particle swarm optimization algorithm (MLP-PSO). Data preparation prior to executing the algorithms involves applying a Savitzky–Golay (SG) smoothing filter to remove noise from petrophysical well-logs and drilling data from the mud-logs. A genetic algorithm is applied to tune the machine learning algorithms by identifying and ranking the most influential input variables on ROP. This tuning routine identified and selected eight input variables which have the greatest impact on ROP. These are: weight on bit, bit rotational speed, pump flow rate, pump pressure, pore pressure, gamma ray, density log and sonic wave velocity. Results showed that the machine learning algorithms evaluated all predicted ROP accurately. Their performance was improved when applied to filtered data rather than raw well-log data. The MLP-PSO model as a hybrid ANN demonstrated superior accuracy and effectiveness compared to the other ROP-prediction algorithms evaluated, but its performance is rivalled by the SVR model.

Determination of petrophysical parameters from surface measurements of drill cuttings, rather than well logs, has long been a subject of interest in the petroleum industry. Analysis of cuttings is presently included in mud logging workflows, although the methods employed tend to be labor-intensive and inefficient with an emphasis on qualitative lithological and mineralogical descriptors. Nuclear magnetic resonance (NMR) has the potential to deliver rapid formation evaluation at the rig site for near-real-time completion decisions. Despite numerous efforts to demonstrate NMR cuttings analysis, dating back to the 1980s, the technique has yet to achieve commercial success. We suggest this failure is due not to the physics of the measurement, which is understood, but rather to inadequate sample preparation. By centrifuging brine-saturated cuttings from conventional formations under a per-fluorinated oil, and using multinuclear NMR to measure liquid volumes, we obtain accurate porosity and permeability values independent of other measurements. Our robust workflow removes the inconsistencies associated with manual sample preparation. We present two case studies and the important requirements for handling actual drill cuttings.

The objective of this paper is to propose a brand new drilling 3D visualization solution based on WebGL and describe the architecture and application of the cross-platform drilling 3D Visualization Software. The software is part of the Engineering Technology Internet of Things (IoT) System, interfacing with other software and also capable of direct hardware interfacing for data retrieval and system control. It is fully web-based, real time and used in RTOC (Real-Time Operating Center) of IoT system which is a software system for drilling process remote monitor and decision. The data acquired from rig sites is remote transmitted to the data center and analysed in the RTOC, the exports in RTOC use many software do the monitoring and analyzing, if there’s some problems, they can quickly give advices to rig sites. It can put borehole trajectories, LWD, MWD, mud logging, well logging, seismic slice, and formation tops all into a 3D scene, by rotating and zooming, thus experts can get realistic underground scenes. It provides a convenient way to viewing real-time 3D drilling scene in the mainstream browsers on difference systems and devices. The web-based 3D visualization of drilling, LWD, MWD and geological data greatly improves the efficiency of drilling process monitoring and decision-making. Contrast with traditional desktop software, this solution does not need install and can supports all mainstream operating systems, such as Windows, Linux, macOS, iOS and Android, it’s a more lightweight and economical solution.

Glauconite develops widely in T Member in Oriente Basin, Ecuador. The presence of Galuconite reveals the information that can help to determine the sediment environment. However, the distribution of glauconite also makes the pay zone identification of glauconitic sandstone difficult in oilfield operation in many ways. Detailed core data analysis of glauconitic sandstone, include core description, thin section observation, porosity and water saturation, has been performed. The core data indicates that sediment environment changed from coastal estuary to open shelf during the deposition of T Member. The PEF and RHOB data from conventional well logs have been selected to estimate the concentration of glauconite based on the correlation with observation of thin section of core. And porosity estimation can be improved by using various matrix density with consideration of concentration of glauconite, which shows better result than using regular uniform matrix density by comparison with core data. Further, water saturation of glauconitic sandstone can be improved. And gas log data from mud logging has been introduced in pay zone identification of glauconitic sandstone. The combination analysis of well log data and gas log data can improve the determination of pay zone of glauconitic sandstone. The practice in oilfield proves the effectiveness of this method.

Business and government have expressed the need for rapid analysis without a delay for sample transport and processing. Suspected arson cases and chemical spills may require on-site analysis to affect immediate response for detection and hazard mitigation. Potential threats to national security have intensified the need for sensitive and reliable field-portable chromatographic instrumentation. Commercial applications for portable gas chromatographs include “mud logging” for oil and gas well drilling and the analysis of gases contained in transformers to determine the risk of failure. Low power consumption sample processing, column programming, detection systems, and data handling have combined to reduce the size and weight of GCs for portable use. The simplest may consist of little more than an ambient-temperature injector, column, and detector, while the most complex may have every feature of an advanced laboratory instrument. Portable GCs may be based on semiconductor chip processing or assembled from discrete components.

The Sinian Doushantuo Formation is the oldest shale gas reservoir discovered in the world, which contains good shale gas shows as the Eyangye-1 and Zidi-1 wells in the Yichang Region of western Hubei province, China. The shales in the Doushantuo Formation feature considerable thickness (135 m), high gas content (4.83 m3/t) and high fragile mineral content (up to 75%). Due to the influences of the sedimentary environment, the shale reservoirs here have high dolomitic content (54%) and abruptly changes in vertical lithofacies. Moreover, the characteristics of the shale sweet-spot differ significantly from that in the Wufeng Formation and Longmaxi Formation in southeast Sichuan Basin. A high-resolution sequence stratigraphic correlation was performed on the shales of the Doushantuo Formation at the Eyangye-1 well, Zidi-1 well, Zidi-2 well and some outcrop profiles in Yichang area for the identification of their sedimentary microfacies characteristics. A comprehensive comparative analysis was made by incorporating the elemental geochemistry, wireline and mud logging data of the well to further identify the sweet-spot interval therein. With the analysis of Eyangye-1 well, the sweet-spot interval of the Doushantuo Formation is 3360−3408 m, of which sedimentary microfacies is deepwater reduced environment with many pyrite laminaes, and the TOC is high to 3.42%, the Ro is 3.3%, the organic and matrix pore are well developed and the aperture more than 50 nm, the porosity is 2.7%, the desorption gas content average is 2.16%, and the main mineral is dolomitic (54%) and siliceous quartz (21%). Additionally, these parameters combined with previous studies will shed light on evaluating and characterizing the layers therein, also provide referential geological data for the following exploration and development activities of this shale system.

Underground strata are reflected in various information sources in petroleum exploration, including good logging and drilling data. Real-time measurement parameters obtained from mud logging can provide data support for the early discovery of oil and gas resources and the prevention of safety accidents. It plays a forward-looking role in the drilling process. In this paper, we aim at the defection of fuzzy and random characteristics of the big data of drilling element parameters in the current drilling process. A new method named grey wolf optimization-support vector machine (GWO-SVM) is proposed by analyzing the relationship between logging data and formation to solve the serious problem of formation misjudgment. Using element content and Gamma-ray value, data mining is performed by a large number of real-time data obtained from the drilling site. The obtained information is used for comprehensive estimation and prediction of strata. First, the data is normalized, and then, the best $\zeta $ and $\sigma $ values are found through the optimization of gray wolf algorithm, next the SVM training is carried out, finally, the formation prediction model is established, and the error analysis of the results was conducted. In the paper, the algorithm model is subsequently applied to three actual wells. The GWO-SVM model based on drilling data is used to predict the formation, and the error analysis showed that the error range of the GWO-SVM algorithm is within 10%. Compared with the GWO-SVM, the model accuracy of SVM, Particle Swarm Optimization-Support Vector Machine (PSO-SVM) algorithm is lower 53% and 23%, respectively. The GWO-SVM has higher robustness, reliability, and achieves faster convergence speed, stronger generalization effect, and improves the identification accuracy of elements for the formation. The average accuracy of the GWO-SVM in stratum dynamic identification is 93.5%. This model is implemented to support the logging system to improve application strength.

Prediction of penetration rate (ROP) is important process in optimization of drilling due to its crucial role in lowering drilling operation costs. This process has complex nature due to too many interrelated factors that affected the rate of penetration, which make difficult predicting process. This paper shows a new technique of rate of penetration prediction by using artificial neural network technique. A three layers model composed of two hidden layers and output layer has built by using drilling parameters data extracted from mud logging and wire line log for Alhalfaya oil field. These drilling parameters includes mechanical (WOB, RPM), hydraulic (HIS), and travel transit time (DT). Five data set represented five formations gathered from five drilled wells were involved in modeling process.Approximatlly,85 % of these data were used for training the ANN models, and 15% to assess their accuracy and direction of stability. The results of the simulation showed good matching between the raw data and the predicted values of ROP by Artificial Neural Network (ANN) model. In addition, a good fitness was obtained in the estimation of drilling cost from ANN method when compared to the raw data.

By means of chemical combination between the Polydimethylsiloxane (PDMS) layer and Polyethersulfone (PES) layer, a kind of PDMS/PES composite membrane was prepared for separation of the light hydrocarbon components from the drilling mud. Meanwhile, its separation performance of the light-hydrocarbon components from the drilling mud was investigated and evaluated quantitatively. Results showed that the prepared PDMS/PES composite membrane had good mechanical performance, and it was resistant to corrosion of the water-based drilling mud. The PDMS/PES composite membrane can work stably at 5 MPa and 393 K. The responding time of the membrane to sudden change of the hydrocarbon gas content was less than one minute. For either single phase flow or gas-liquid two-phase flow, a high flow rate was recommended to avoid non-ideal flow patterns and to increase mass transfer in the feed channel of the membrane cell. Results in this work could be helpful for further application of the membrane technology in geological mud logging.

It is proved that the Wufeng-Longmaxi formation in Sichuan Basin is the key shale gas layer in China. Although the breakthrough of shale gas exploration had been gotten in it, the enrichment mechanism of it has not been well studied. To understand the enrichment mechanism of it, we will take the biggest total gas content layer (BTGC layer) and main production layer (MP layer) drilled in well HD-1 for example. A series of experiments were conducted on core samples, including total organic carbon (TOC) content, X-ray diffraction (XRD), scanning electron microscope (SEM), focused ion beam scanning electron microscope (FIB-SEM) and Micro-CT. Meanwhile, the aid tests (such as mud logging data, reservoir physical test, field desorption experiment data, mud gas logging data) were integrated to study the difference of the two sections in gas storage and transmission capacity too. The results show that although the field desorption gas content of BTGC layer is bigger than MP layer, the TOC of BTGC layer (3.45%) is smaller than it in MP layer (4.15%). The MP layer is dominated by the quartz with average value 87.3% which is obviously bigger than it in BTGC layer 37.5%. Although the helium porosity in BTGC layer (2.98%) is bigger than MP layer (2.68%), the permeability of it(0.005878mD) is smaller than MP layer(0.013950mD). Except the organic pores, to a certain type, the pores in the MP layer are bigger than them in BTGC layer, such as interparticle pores, dissolution pores, micro fractures. The connected pores are dominated by the pores in mm-scale and micro-scale. The difference of the enrichment mechanism in the two layers is dominated by the difference of pore structure. The MP layer provides a migration pathway to the gas enriched from nearby shale layer in km-scale. If the permeability and the overpressure of the layer are big enough, the shale gas would be exploited without hydraulic fracturing. In BTGC layer, the pores are scatted in the shale and isolated from each other. The gas storage ability of this type is commonly good, with high field desorption gas content, but it must be exploited with hydraulic fracturing for its low permeability. It is need to pay attention to the high permeability layer in shale strata in the further exploration of shale gas.

We present hydrogen gas concentration data for drilling mud extracted during the Wenchuan Earthquake Fault Scientific Drilling (WFSD; holes 2 and 3), measured on-line during drilling in SW China. Hydrogen influx into the well at depth is largely dependent on lithology and fracture density. In hole WFSD-2, the average background concentration of hydrogen is lower in granitic rocks than in sedimentary formations. More than five major hydrogen influxes were detected while drilling through the sedimentary formations, and two hydrogen-rich zones were detected in the granite (1240–1243 m and 1383.5–1405 m depth). In hole WFSD-3, mud extracted from a tectonic breccia contains high hydrogen concentrations at depths of 600–1000 m depth, and relatively low concentrations below 1000 m depth. In both holes, we observe a lack of hydrogen in the center of the fault zone and high concentrations of hydrogen in fractured zones. Hydrogen concentration in both holes displays significant vertical heterogeneity, and is positively correlated with fracture density. Hydrogen was likely sourced from interaction between water and fresh silicate minerals surfaces that were exposed during faulting, from the mantle, and from faulting events. Fracture zones provide the main channels for the migration of hydrogen gas. The variations in background hydrogen concentrations relate to changes in porosity and permeability. The two hydrogen-rich zones (642.36–676.22 m, and 1383.5–1405 m) were likely caused by earthquake activity or far-field triggering during WFSD-2 drilling. The results of this study provide gas data that can be used to model fault activity. It is important to consider the relationship between hydrogen gas and the seismic cycle, and to use such data to identify seismic precursors.

Rate of penetration (ROP) enhancement serves as a key factor in reducing drilling time and hence drilling costs. ROP enhancement requires identification of the parameters affecting this rate. However, the large number of effective parameters, which are further immersed in noise, makes it difficult to present a highly accurate and comprehensive model. In the present research, in order to predict the drilling ROP in one of the vertical wells drilled into the Karanj Oilfield, a hybrid model composed of a multilayer perceptron (MLP) neural network together with either a particle swarm optimization (PSO) algorithm or a cuckoo optimization algorithm (COA) was used. For this purpose, first petrophysical logs and drilling data were denoised using the Savitzky–Golay filter. Then, the 'plus-l-take-r' method was used to select superior features. Feature selection results indicated that an increase in the number of input parameters tends to reduce the error associated with the estimator model; however, the error reduction rate was seen to be negligible for models with five or more input parameters. Therefore, five parameters were considered as input parameters in MLP-COA and MLP-PSO hybrid models: rotary speed, weight on bit, shear wave slowness, compressional wave slowness, and flow rate. A comparison of errors and coefficients of determination in the training phase of the two models indicated that MLP-COA model tended to converge way faster and more accurately. The small difference in generated error using this model between training and testing phases indicated the high reliability and generalizability of the model. Comparing the results of the model trained with raw and denoised data against the same set of selected features clearly showed the positive effect of the denoising step on the accuracy of the model. Validation of the proposed model via the multilinear regression method was indicative of the superior performance of the MLP-COA model, so that it could be confidently stipulated that this model can be used to estimate the ROP at other vertical wells near the studied well. Further, provided the required information is available, this method can predict the ROP to high accuracy in vertical oil and gas wells.

Cuttings transport becomes critical important when horizontal directional drilling (HDD) technology has been used more often in long distance and large diameter oil and gas pipeline construction in rocks. Front reaming (FR) and one way drilling mud return (OWDMR) were not new in oil and gas well drilling, but they were rarely used in HDD industry compared to the traditional back reaming (BR) and two way drilling mud return (TWDMR). FR and OWDMR technologies, when they were used in HDD, were designed mainly for highly non-leveled HDD projects to overcome some difficulties such as the recycling of drilling mud. Along with these technologies is that the cuttings need to travel longer distance to the ground surface. In addition, the effect of the drill rod rotation on the cuttings transport does not exist because hole bottom mud motor is usually used in FR. To find a solution for this problem, the cuttings transport mechanism was analyzed based on the drilling mud hydraulics, and then, an equation of cuttings transport distance was derived. It found that the average drilling mud velocity in the annulus and the consistency index of drilling mud are the two most important factors related to the cuttings transport distance. To help with the cuttings transport, a new MMH drilling mud system, which provides a high consistency index and a low flow index, was used in rock HDD projects, instead of the common Bentonite-water drilling mud system.

The drilling mud loss risk is a major problem for horizontal directional drilling (HDD) projects when it was drilling in fractured rock stratum. The existing theoretical calculation methods for the maximum allowable drilling mud pressure in HDD borehole are particularly designed for soils, so they are not suitable when rocks are encountered. The maximum allowable drilling mud pressure was analyzed in this study for a fracture zone of a maxi-HDD project crossing Yangtze River. The geotechnical investigation disclosed multiple layers of soils and rocks: the upper part two sand layers and the lower part one sandstone layer. The fracture zone in the sandstone layer was investigated by digital panoramic borehole camera technique, so that the detailed fracture orientations and locations can be identified. The maximum drilling mud pressure for the upper part two sand layers was calculated using Delft equation. At the same time, the evolution of drilling mud pressure in the fracture zone was studied using numerical modeling method. Combing with the calculation results of both Delft equation and numerical modeling, the maximum allowable mud pressure at the fracture zone of the HDD borehole was obtained. The numerical modeling found that the persistent fracture system in the fracture rock mass has very low resistance to the drilling mud pressure propagation, so a low drilling mud pressure needs to be used when it was drilling/reaming in the fracture zone. The effects of fracture aperture, the drilling mud viscosity, and fracture roughness on the mud pressure evolution were also analyzed.

Mud logging system presents the most promising tool for exploring oil and gas resources, which relies on the multi-component analysis of gases to evaluate the hydrocarbon reservoirs. Higher detection efficiency, especially relating to the high-throughput analysis, can offer an important means to enhance the oil and gas recovery of hydrocarbon reservoirs. However, fewer technologies can measure both hydrocarbon and non-hydrocarbon gases in a timely manner. In the present work, a method based on data driven Raman spectroscopy (DDRS), which allows simultaneously accurate analysis of 12 hydrocarbon and non-hydrocarbon gases, has been proved. By developing a data driven strategy that incorporates higher-density discrete wavelet transform (HDWT) and template oriented frog algorithm (TOFA), the spectral resolution of Raman spectroscopy was significantly improved in both time and frequency domains to extract the target gas information from the Raman spectra, facilitating the detection of hydrocarbon reservoir. Theoretically, it is considered that the DDRS represents a promising tool for extracting the quantitative information from multi-component gases in the presence of dominantly uncontrolled variance. Our work has tested and refined the DDRS by performing a comprehensive analysis of three gas mixtures established to yield challenges representative of those encountered in a common mud logging analysis. The DDRS compared favorably with the gas chromatography (GC) method. The satisfactory results indicated that the DDRS has the capability to continuously detect 12 hydrocarbon and non-hydrocarbon gases in real time, which could be extended to online multi-component analysis of any other gas and fuel systems.

To control the human factor risk for oil and gas drilling industry, the types of work activities involved in drilling were identified, the major accident risk types of human errors were selected, the probability and severity levels of the risks associated with each activity were quantified, and the human factor risk levels of major work activities involved in drilling processes were calculated. Quantitative results demonstrate that the highest risks during the drilling process include being struck by an object, injury by machine, and overexertion; conversely, the lowest risks include exposure to harmful substances or environments and fire and explosion. The highest risk activities are associated with, for instance, penetration drilling, the trip in and out, and the hoisting and lifting operations. Conversely, the relative lowest risk activities include auxiliary operations, well logging and mud logging, equipment inspection and maintenance. The total risk value of all main drilling activities is 11.3947 S/w-h. Twelve risk control measures were selected, and the Delphi method was taken to quantify the human factor risk mitigation capacity resulting from the selected risk control measures. The results demonstrate that the human risk control measures exist in three tiers of effectiveness, with each tier being separated by nearly an order of magnitude. The types of most risk mitigation are risk codes, such as injury by machine, fall from height, and contact with harmful material. The most minimal risk mitigation types include muscle strain and fire and explosion. Finally, these data will be valuable for drilling companies to strategically allocate limited resources to their safety management plan, and they can evaluate the expected effectiveness resulting from risk control measures.

Demand of the oil and gas energy is increasing very drastically. Conventional hydrocarbon reservoirs contain below the sealing cap rock (shale) and easily move towards wellbore are at the depletion stage. Therefore, drilling engineers in collaboration with mud engineers, geologists and geophysicists are looking for innovative materials to drill unconventional hydrocarbons reservoir which are distributed at the basin scale and cannot approach easily. Geo-thermal energy wells and most of unconventional reservoirs are occurred at high pressure high temperature (HPHT) conditions. Conventional micro-macro organic drilling mud additives with heat insulator in nature can minimize efficiency while drilling HPHT wells. Oil-based muds (OBM) are strictly restricted due to high toxic level and poor emulsion stability at HT. However, this review suggests that addition of macro size organic particles and inorganic nanoparticles can enhance rheological performance, reduce filtrate loss volume and improve shale inhibition characteristics of environmental friendly water-based mud (WBM). Despite an impressive amount of experimental work has been done over drilling additives and their effect over rheological and shale inhibition, taking into account their literature review are rare. In addition, there is no review work of the knowledge gained to date. This work will hope fully trigger further development and new research topics in the area of drilling muds system.

The present work is devoted to study the geologic setting, reservoir characterization and hydrocarbon detection with conventional and advanced well log methods for Kafr El-Sheikh Formation at Sapphire field, Offshore Nile Delta, Egypt. The used wells are Sapphire-Da, Db, Dc, De, Dh and Dq. By using open hole logging tools, advanced logging tool like Modular dynamic tester (MDT), Mud log during drilling and conventional core that analyzed carefully, to detect the clean sandstone and thin bedded sandstone of the study Location. These basic well log tools (Gamma Ray, Resistivity, Density and Neutron) reflectclean sandstone reservoir with good way, but can’t detectthin bedded sandstone reservoir, as a result of their low vertical resolution, this may miss several intervals charged with hydrocarbons during perforation and production from the field.So, we should run advanced tool like the Modular Dynamic Tester (MDT) and analyze conventional core, if found, and the hydrocarbons in Mud log to detect these missed intervals. Also by using the conventional cores and mud logging while drilling. The results had showed clean sandstone and thin bedded sandstone reservoirsthroughthe advanced well log tools, which identify more than 68% deep water reserve didn’t use beforethis should be takeninto consideration in the future wells, workover wells, excellent distribution of facies in both the static and dynamic models, to increase the hydrocarbon production and life time of producible wells. . The optimum location for forthcoming wells is south west of the field, because it has the best petrophysical parameters. It has high porosity, hydrocarbon saturation, and net to gross, in addition to low shale volume.

High-yield gas layers, low-yield gas layers and (gas bearing) water layers of Upper Paleozoic coexist in the Shilijiahan zone in the northern Ordos Basin, but gas–water distribution characteristics, laws and influence factors are not understood well, so the exploration and development of natural gas in this zone are restricted. In this paper, statistical analysis was carried out on the data of Upper Paleozoic formation water in this zone, e.g. salinity, pH value and ion concentration. It is shown that the formation water in this zone is of CaCl 2 type. Then, the origin, types, controlling factors and spatial distribution characteristics of formation water were figured out by using core, mud logging, well logging and testing data, combined with the classification and evaluation results of geochemical characteristics of formation water. Besides, the logging identification chart of gas, water and dry layers in this zone was established. Finally, the occurrence and distribution laws of reservoir fluids were defined. The formation water of CaCl 2 type indicates a good sealing capacity in this zone, which is favorable for natural gas accumulation. It is indicated that the reservoir fluids in this zone exist in the state of free water, capillary water and irreducible water. Free water is mainly distributed in the west of this zone, irreducible water in the east, and capillary water in the whole zone. The logging identification chart has been applied in many wells in this zone like Well Jin 86. The identification result is basically accordant with the gas testing result. It is verified that gas and water layers can be identified effectively based on this logging identification chart.

The utilization of traditional chemicalS added substances to control drilling mud characteristics overwhelmingly negatively affect people and the environment, they are originally utilized to help control/regulate the seepage loss, the rheological properties, or other physical specifications. Utilizing eco-friendly and biodegradable options are not just more secure than customary strategies yet demonstrates no damage to drilling personnel and is more economically practical than traditional techniques. A conceivable alternative for biodegradable and eco-friendly added substance is including differing concentrations of banana peel powder (BPP) to water-based mud. To test the impacts of BPP in water-based mud, three distinct investigations were led utilizing different grouping of BPP. Utilizing low-temperature and low-pressure (LTLP) API standard tests for drilling fluid, the readings were effectively recorded to comprehend the effects of BPP added materials on the mud attributes. The seven testing procedures performed were rheometer/viscometer, LTLP filtration, mud balance, chemical titration, resistivity device, and pH and temperature tests. Looking at the experimental findings, 1% (6 gm), 2% (12 gm), and 3% (18 gm) were first evaluated at room temperature and pressure. Adding BPP showed little to no effect on the mud density. However, for the rheological properties, the experimental additives resulted in increasing plastic viscosity (PV), yield point (YP), especially at 3% concentration. The BPP also showed excellent behavior for the initial and final gel strength as compared to the reference mud. Other properties that remarkably reduced were the pH levels and mud resistivity, which decreased as more BPP was added. The experimental mud filtration at 7.5 minutes and 30 minutes also showed a great improvement along with the filter cake thickness proving it to be a multipurpose effective drilling additive for water-based fluids. Additionally, other properties such as temperature, which was not affected, salinity (NaCl) and calcium content (Ca++) changed due to the increase in BPP concentration. The salinity was significantly increased for the mud, mud cake, and mud filtrate; while the calcium content was decreased from 52 mg/L to 8 mg/L by introducing 3% BPP additive. After experimenting with different concentrations of BPP, it can be concluded that there was an overall improvement in the mud's properties. The outcomes and economic evaluation of the BPP revealed that it can possibly be used as biodegradable drilling fluid additives other than conventional chemical additives. Considering the outcomes recently expressed demonstrating the decrease in pH, filtration specifications, and Ca++; while increasing in viscosity and NaCl properties. This work traces the probability of moving towards BPP as a biodegradable drilling fluid additive that is more financially feasible elective, than conventional chemical additives. BPP is by all accounts an increasingly reasonable choice moving ahead later on.

The central paleo-uplift belt of the Northern Songliao Basin, as one major region of risk exploration of natural gas, has favorable conditions for natural gas accumulation. However, one of the main reasons why no breakthrough has been achieved was the unclear studing of reservoir characteristics. Based on core, mud logging, well logging, 3D seismic, the characteristics of basement rock reservoirs in central paleo-uplift belt were discussed from the perspective of lithological characteristics, physical characteristics and reservoir spatial characteristics, and proposes new four cognitions: ① the lithology of the basement rock reservoirs were complex, the reservoir was dominated by granite, metamorphiterocks; ② Reservoir heterogeneity was relatively strong and matrix porosity was low, indicating a tight reservoir; ③ the types of reservoir space included mainly fractures and dissolution pore, three reservoir types of pore-fracture type, fracture-hole type and fracture type were clearly defined. The pore-fracture type reservoir was the most favorable reservoir type in the basementrock potential mountain; ④ The controlling factors of reservoir development of basement included tectonics, lithology, weathering leaching and magmatic intrusion. The lithology, weathering leaching and fracture were the most important influencing factors of weathering reservoir. The horizontal well of LP1 of granite weathering crust reservoir was advanced, and the output breakthrough was obtained. It greatly expanded the space for natural gas exploration, strengthened the confidence of the new field to achieve a major breakthrough, and pointed out the direction for the long-term development of risk exploration in the new field of Daqing Oilfield.

The use of conventional chemical additives to control drilling mud specifications causes serious health, safety, and environmental side effects. To mitigate these lasting hazards, an economic multifunctional bioenhancers should be exploited as additives in place of the traditional materials to achieve the desired drilling mud properties. Using a bioenhancer is not only safer for the environment, but it poses no risk to drilling personnel and is more cost-efficient than conventional methods. In this work, two concentrations of is Palm Tree Leave Powder (PTLP) were added to the base mud and drilling fluid properties were measured. The pH test demonstrated PTLP's ability to minimize alkalinity. At 1.5% (11 gm) PTLP, the pH was decreased by 21%, while 3% (22 gm) PTLP showed a reduction of 28%. A reduction in seepage loss (cc/30min) of 26% and 32% was also observed, respectively, when comparing it to the reference fluid. Simultaneous improvement of the mud cake was seen over the reference fluid, signifying PTLP could also substitute fluid loss control agents. The plastic viscosity (PV) of the reference fluid was insignificantly affected by the introduction 1.5% (11gm) PTLP. However, when the concentration of PTLP was increased to 3% (22 gm) a tangible increase in PV was seen due to the inefficient grinding of the palm tree leaves (PTL) and irregular dispersal of particle sizes. To mitigate this, a more effective form of grinding for PTL is needed as well as a sieve analysis to ensure equal distribution of particle sizes. The second component of viscosity, yield point (YP), was drastically reduced by 59% at both 1.5% (11 gm) and 3% (22 gm) as compared to the reference fluid. Additionally, initial and final gel strengths were significantly reduced at both concentrations. These results are an indicator that PTLP can be a viable option as a thinning material for water-based mud. Considering the previously stated results, PTLP can be a feasible replacement or at least supportive material for conventional pH reducers, filtration loss control agents, and viscosity thinners. This biodegradable drilling mud additive shows great potential and is a practical option to replace or at least support toxic chemicals traditionally used such as lignosulphonate, chrome-lignite, and Resinex. This work outlines a practical guide for reducing drilling fluid costs as well as the impact on drilling personnel and the environment.

This paper presents the utilization of advanced mud logging to support drilling of horizontal well on the Ignyalinsky license area of Eastern Siberia. The advanced mud logging complex includes specialized software for recording and analysing geological and technical drilling parameters; technological sensors for registration of drilling parameters with the permissible limits of errors no more than 1%; advanced gas logging by using a high-resolution chromatograph at suction and return lines; geochemical analysis devices for XRF, XRD cuttings analysis and natural gamma radiation analysis of cuttings; the use of cuttings weighing machines to quantify the degree of the wellbore cleaning. This article discusses the application of listed data for geosteering and clarifying the geological model of the reservoir. The lithological analysis of cuttings is carried out on the base of mineral and elemental cuttings composition, which, unlike field data of a standard mud logging survey, exclude the concept of "human factor" during analysing the lithology of cutting samples. The data on mineral and elemental composition of wells were interpreted to clarify the lateral variability of the reservoir and to highlight potential reservoir intervals. Advanced gas logging was used to identify potential reservoir interval in pilot well, and consequently to plan MDT works. Data on elemental composition of cuttings sample from pilot section and from core analysis of nearby exploration wells were used to construct geochemical profile of the reservoir. Furthermore, reference chemical elements were selected to mark the well position in the reservoir: exit above or beneath the target interval. XRF elemental analysis while drilling was used to improve borehole position in conjunction to LWD data. The elemental composition of cuttings of horizontal well were used for facial interpretation, which is not captured by LWD tools. So, ancient fluvial channel bodies were identified on the base of geochemical rock typing, and potential reservoir intervals are suggested. The performed interpretation was verified by the resultsof the multistage hydraulic fracturing.

The main objective of this paper is to develop a new material used to control the seepage losses and combat issues regarding thick mud cake. The plan is to develop a biodegradable waste material from Grass, which is environmentally friendly to be utilized as an alternative material to address filtration problems. Raw material from local Grass in the USA was used to construct the fibrous fluid loss control agent (Grass Powder). The lab procedure consisted of crushing and grinding process to assemble the samples to be ready for preparation. Spud mud samples were used as a guide to indicate filtration control. The material was tested to generate results from the experiments conducted at surface conditions to determine the reduction in the volume of filtrate and mud cake. Based on the experiments conducted, Grass Powder (GP) can be applied to treat problems associated with the seepage loss in the drilling operations. The grass availability, being eco-friendly, low cost, and the simple method of Grass Powder preparation by using grinding and crushing can prove to be a suitable replacement for conventional materials used to control filtration. Then, the results of Grass Powder were compared to starch, commonly used conventional additive. The results showed that Grass Powder decreased the fluid loss by 44% at 1% (7 grams) concentration of GP, and the filter cake was enhanced as well when comparing it to the reference fluid. While the starch material showed an improvement in seepage loss by 40% at 1% (7 grams) concentration when comparing it to the reference fluid. In addition, starch was less efficient in improving the filter cake as compared to Grass Powder. Consequently, GP laboratory outcomes slightly showed better performance as compared to starch additive, suggesting the feasibility of Grass Powder to be used as fluid loss control agents. In brief, these experimental results exhibit that Grass Powder has the potential to be utilized as biodegradable drilling fluid additives replacing chemical additives and reducing the amount of non-biodegradable waste disposed to the environment.

Borehole-log data acquisition accounts for a significant proportion of exploration, appraisal and field development costs. As part of Shell technical competitive scoping, there is an ambition to increase formation evaluation value of information by leveraging drilling and mudlogging data, which traditionally often used in petrophysical or reservoir modelling workflow. Often data acquisition and formation evaluation for the shallow hole sections (or overburden) are incomplete. Logging-while-drilling (LWD) and/or wireline log data coverage is restricted to mostly GR, RES and mud log information and the quality of the logs varied depending on the vendor companies or year of the acquisition. In addition, reservoir characterization logs typically covered only the final few thousand feet of the wellbore thus preventing a full quantitative petrophysical, geomechanical, geological correlation and geophysical modelling, which caused limited understanding of overburden sections in the drilled locations and geohazards risls assessment. Use of neural networks (NN) to predict logs is a well-known in Petrophysic discipline and has often used technology since more than last 10 years. However, the NN model seldon utilized the drilling and mudlogging data (due to lack of calibration and inconsistency) and up until now the industry usually used to predict a synthetic log or fill gaps in a log. With the collaboration between Shell and Quantico, the project team develops a plug-in based on a novel artificial intelligence (AI) logs workflow using neural-network to generate synthetic/AI logs from offset wells logs data, drilling and mudlogging data. The AI logs workflow is trialled in Shell Trinidad & Tobago and Gulf of Mexicooffshore fields. The results of this study indicate the neural network model provides data comparable to that from conventional logging tools over the study area. When comparing the resulting synthetic logs with measured logs, the range of variance is within the expected variance of repeat runs of a conventional logging tool. Cross plots of synthetic versus measured logs indicate a high density of points centralized about the one-to-one line, indicating a robust model with no systematic biases. The QLog approach provides several potential benefits. These include a common framework for producing DTC, DTS, NEU and RHOB logs in one pass from a standard set of drilling, LWD and survey parameters. Since this framework ties together drilling, formation evaluation and geophysical data, the artificial intelligence enhances and possibly enables other petrophysical/QI/rock property analysis that including seismic inversion, high resolution logs, log QC/editing, real-time LWD, drilling optimization and others.

The complex nature of the reservoir dictated comprehensive formation evaluation logging that was typically done on wireline. The high angle designed for maximum reservoir exposure, high temperature, high pressure (HTHP), differential reservoir pressure and wellbore stability challenges necessitated a new approach to overall formation evaluation. The paper outlines Formation Evaluation strategy that reduced risk, increased efficiency and saved money, while ensuring high quality data collection, integration and interpretation. After review of all risks, a decision to utilize Managed Pressure Drilling (MPD) for wellbore stability, Logging While Drilling (LWD) to replace wireline and Advanced Mudlogging Services was implemented. The Formation Evaluation team utilized LWD resistivity, neutron, density and nuclear magnetic resonance logs supplemented with x-ray diffraction (XRD), x-ray fluorescence (XRF) and advanced mud gas analysis to ensure comprehensive analysis. The paper outlines workflows and procedures necessary to ensure all data from LWD, XRF, XRD and mud gas are integrated properly for the analysis. Effects of Managed Pressure Drilling on mud gas interpretation as well as cuttings and mud gas depth matching are addressed. Depth matching of all data, mud gasses, cuttings and logs are critical for detailed and accurate analysis and techniques are discussed that ensure consistent results. Complex mineralogy due to digenesis and effect of LWD logs are evident and only reconciled by detailed XRF and XRD data. The effects of some conductive mineralogy are so dramatic as to infer tool function compromise. The ability to determine acceptable tool response from tool failures eliminates unnecessary trips and leads to efficient operations. The final result of the above data collection, QC and processing resulted in a comprehensive formation evaluation interpretation of high confidence. Finally, conclusions and recommendations are summarized to provide guidelines in Formation Evaluation in similar challenging highly deviated, HTHP, complex reservoir environments on land and offshore.

The high costs and high potential risks associated with drilling deepwater wells have prompted the development of an advanced computerized mud logging system. This paper highlights select technologies within the system and its application to three core areas of operation—circulating, making connections, and tripping—to provide early identification of fluid influxes and losses, thus helping ensure safe and efficient well delivery. The advanced mud logging system includes a kick-detection system, flowback monitoring, trip monitoring software, and mud accounting software based on a new methodology. The kick-detection system uses advanced flowmeters to enable stricter control of the drilling process; fluid influxes or losses are detected by integrating the variance for predicted and measured flow and alarming, with as little as a barrel gained or lost. Flowback monitoring uses sophisticated algorithms in conjunction with the same high-accuracy flowmeters to monitor influxes while making connections. These algorithms drive a complex alarm system tuned to trigger on minimal flow variance, pit volumes, and the rate of modification of each compared to a historical baseline. Additionally, trip-monitoring software automates the tracking of pipe displacements in real time to warn of a well control event, instead of relying on spreadsheets or handwritten calculations. Mud accounting software tracks drilling fluid balance across the entire pit system for redundant influx and loss detection and accounts for volume changes based on circulating rates. Application of the advanced mud logging system in the deepwater Gulf of Mexico (GOM) provided earlier detection of well control events—up to 10 minutes earlier than conventional well monitoring techniques. Flowback monitoring demonstrated the ability to identify minimal flow when making connections, which would be difficult to detect by visual inspection. The ability to trend flowback profiles consistently has allowed operators to reduce the pump's off time while making connections in less than 5 minutes, without jeopardizing the ability to confirm a static well. Additionally, the advanced system enables drilling operations to proceed without increasing mud weight and exacerbating wellbore damage during a ballooning event. This paper presents a case study in which the history of well control events documented in the literature was reviewed to help identify areas of improvement.

Conventional chemical additives used in controlling drilling fluid properties have a severe drawback on the environment and personnel safety. The commercially available additives are non-biodegradable materials and have negative impacts when released to the environment. Thus, there is a great need for new environmental friendly biodegradable drilling fluid additives that can help to control the drilling fluid properties with the least effects on the environment and the workers’ health. This study investigates the introduction of biodegradable food waste product, which is Potato Peels Powder (PPP) to be used as environmental friendly drilling fluid additive. The effects of adding various concentrations of PPP on the chemical and the physical properties of the drilling mud (e.g. mud weight (MW), plastic viscosity (PV), yield point (YP), the filtration characteristics, and pH) were evaluated. The evaluation included conducting lab experiments with full-set measurements following the specifications of the American Petroleum Institute (API), such as filtration loss and corrosion control rate The effects of adding different concentrations of the bio-enhancer additive (PPP) were measured and recorded using mud balance, a standard API viscometer, a standard low-pressure and temperature (LPLT) filter press, chemical titration, and other drilling lab equipment. Then, all results of PPP were compared with the properties of the reference water-based mud (spud mud) in order to assess and validate the effects of biodegradable additives and their effectiveness in optimizing the performance of water-based mud. The results showed that PPP had a negligible effect on mud weight and solid content. However, PPP tangibly influenced the rheological properties in terms of maximizing plastic viscosity and minimizing yield point and gel strength. Also, PPP significantly improved the filtration characteristics by reducing the fluid loss and mud cake thickness, suggesting their applicability to be used as an excellent fluid loss control agent. Moreover, PPP additives resulted in increasing sodium chloride (NaCl); consequently, resistivity was reduced. Finally, PPP additives resulted in a reduction in alkalinity and calcium ions content (Ca++). These experimental results show that Potato Peels Powder (PPP) has the potential to be used as an alternative to some of the conventional chemical additives, and hence reducing the amount of non-biodegradable waste disposed to the environment, avoiding the personnel safety, and minimizing the drilling cost.

Petrophysical evaluation from laboratory and well logging data, such as gamma ray, Nuclear Magnetic Resonance (NMR) and resistivity has been used to identify and evaluate oil zones in reservoirs. Gamma ray log is able to predict lithologies along the well, and X-ray Diffraction (XRD) and X-ray Fluorescence (XRF) techniques also provide important lithological laboratory information. The NMR log directly estimates the porosity of the rock. Resistivity log identifies the water region, but cannot provide information about oil saturation. However, the application of unconventional techniques, such as Electron Spin Resonance (ESR), can be of great relevance in the well logging, adding information about lithologies, oil quality and saturation. The ESR technique, which can directly estimate the oil saturation inside the rock, can also provide important information about the origin and formation of rocks. This technique could be an advance for the oil industry, helping to understand the geothermal processes suffered by the rocks and identifying important regions of the reservoir. Thus, in this work, we studied carbonate rock (limestone and dolomite) samples with and without oil, by ESR technique. Firstly, the effectiveness of ESR in the differentiation of carbonates (calcitic and dolomitic) without oil was tested, through the analysis of manganese ion impurity, which promotes the replacement of calcium and magnesium ions in calcites and dolomites. The samples had a typical manganese ESR signature. The hyperfine parameter, A, was homogeneous for both limestone and dolomites. The zero-field split parameter, D, showed variability, as reported in the literature. The studies were carried out at X-band frequency. The analysis by XRF and XRD provided information on the chemical and mineralogical composition of the carbonates, which were added to the ESR data for application in a correlation matrix, by which it was identified that the components CaO and MgO were directly related to the intensity of the ESR signal and the concentration of CaO was inversely related to the concentration of Al2O3 and SiO2. In one limestone rock sample was incorporated oil, with 25° API and moderate biodegradation level, to identify by ESR, the oil presence inside this rock. The technique was able to identify the oil and its saturation in the rock through the detection of free radical signal, g = 1.9951. The innovative application of the ESR technique to identify oil in varying saturation, in carbonate rock samples from the Illinois Basin (USA), was successful. These results demonstrated that this technique in addition to being accurate, non-destructive and relatively low cost, could be used in mud logging operations providing results for lithological characterization, oil identification and its saturation inside the reservoirs.

The problem of lost circulation is a direct consequence of the presence of fractures or high permeability. Lost circulation material (LCM) is used to treat the loss that occurs or proactively strengthen the wellbore of the potential loss zones. The polyacrylamide (PAM)/Polyethylenimine (PEI) cross-linkable polymer gel is proven to work best in zone-sealing and plugging applications. In addition to their thermal stability, the fact that these gels are flexible gives them the advantage of deforming and sealing-off multiple and complex near wellbore fractures. The primary objective of this study is to investigate the gelation kinetics of the PAM/PEI cross-linkable polymer to be used in drilling fluids formulations to enhance wellbore stability and strength. Different combinations of polymers and crosslinkers were evaluated; potential polymers were screened for gelation kinetics and gel strength in typical drilling mud formulations. The gelation time of the polymer-based drilling mud formulation is determined in salt-free and in saline systems. The results on rheological properties and gelation kinetics were used to prepare a gelling mud formulation using PAM/PEI cross-linkable polymer as LCM. The produced gel was thermally stable under high-temperature-high-pressure reservoir conditions, which will result in enhanced wellbore strengthening. This paper was made possible by an NPRP Grant # NPRP10-0125-170240 from the Qatar National Research Fund (a member of Qatar Foundation ). The statements made herein are solely the responsibility of the authors. Scopus

Biostratigraphy is a key upstream activity. Drilling operations use biostratigraphic data derived from core samples extracted via boreholes (mud logging) in order to guide drilling processes and verify models of basin geology. Current manual data analysis relies on the existence of sufficient numbers of biostratigraphers to be available to fulfil industry needs. However, due to factors such as retirement, and that the number of people being trained in the requisite taxonomic skills has declined sharply over the last couple of decades; the available pool of expertise is dwindling. It is clear that if the high cost of drilling operations is taken into account, the current situation is untenable and in many ways represents a perfect storm. This pessimistic situation can be radically changed by augmenting human expertise using automated species identification tools based on artificial neural network technology. DAISY [Digital Automated Identification System], a proven system of this sort, could revolutionise commercial biostratigraphy operations by enabling microfossil identification to be undertaken by technicians. This would yield immediate benefits for the industry as it would permit routine work to be performed quickly and accurately by less skilful, cheaper and therefore more available staff; freeing biostratigraphers to concentrate on non-routine, more complex tasks. The feasibility study presented here indicates that DAISY can consistently identify microfossils to species, with repeatable, high levels of accuracy. Crucially, it can also act as a permanent repository for taxonomic knowledge, which is currently lost when experienced personnel retire. There might also be additional environmental and social benefits if this technology is widely adopted within the oil and gas sector: as DAISY technology is generic, it can easily be re-targeted to interpret seismic data or even to estimate the impact of upstream exploration activities on abutting ecosystems.